In general, portable terminal apparatuses include a first housing (fixed plate) provided with numeric keys and the like and a second housing (movable plate) provided with a liquid crystal display unit and the like and allowed to be opened and closed relative to the first housing. Further, common structures for causing the second housing to be opened and closed relative to the first housing include those of a type that connects the first housing and the second housing with a hinge mechanism and causes the second housing to be opened and closed by rotating the second housing relative to the first housing (a folding type) and those of a type that causes the second housing to be opened and closed by sliding the second housing relative to the first housing (a sliding type).
Recent portable terminal apparatuses have become more and more multifunctional, and apparatuses have been provided that are capable of receiving a terrestrial digital broadcast. Liquid crystal display units have also become larger in size. Further, with an increase in the number of functions, the number of keys of a keyboard for making inputs to portable terminal apparatuses also tends to increase, so that the keyboard also tends to become larger in size. Meanwhile, a constant demand for improvement in the portability of portable terminal apparatuses does not allow an unlimited increase in the sizes of liquid crystal display units and keyboards.
The above-described folding-type portable terminal apparatus has a problem in that it is impossible to use a liquid crystal display unit when the portable terminal apparatus is folded because the liquid crystal display unit is hidden when the portable terminal apparatus is folded. While the above-described problem of the folding-type portable terminal apparatus does not occur in the sliding-type portable terminal apparatus, the sliding-type portable terminal apparatus has a problem in that the first housing and the second housing inevitably overlap each other when the portable terminal apparatus is unfolded, thus preventing effective use of space.
Therefore, opening and closing devices have been proposed that cause the first housing and the second housing to be in the same plane (flat) when the first housing and the second housing are opened (see Patent Documents 1 through 3). According to this configuration, it is possible to use a liquid crystal display unit even when the first housing and the second housing are closed, and when the first housing and the second housing are opened, there is no overlap between both housings, so that it is possible to make effective use of space.